a. A solemn, formal declaration or promise to fulfill a pledge, often calling on God, a god, or a sacred object as witness. b. The words or formula of such a declaration or promise.
An oath is supposed to be a statement somehow more special than our everyday speech. Because of the sudden flow of emotion an oath is stated instead of a statement of proclamation. People can swear to another person but may vow only to God.
First let us deal with what The Messiah said:
“Again, ye have heard that it hath been said by them of old time, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths: But I say unto you, Swear not at all; neither by heaven; for it is God's throne: Nor by the earth; for it is his footstool: neither by Jerusalem; for it is the city of the great King. Neither shalt thou swear by thy head, because thou canst not make one hair white or black. But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil” (Matthew 5:33-37).
First of all the need to swear an oath comes from a need for your words to be believed. If you always did everything you said you would, there would be no need for anything more than yea, I will do it; or nay, I will not do it. This is why more than yes or no comes from evil. If you have to swear an oath for your words to be true, then an intelligent person would conclude that any and everything you say when not swearing an oath has a lie contained in it.
“When thou vowest a vow unto God, defer not to pay it; for he hath no pleasure in fools: pay that which thou hast vowed. Better is it that thou shouldest not vow, than that thou shouldest vow and not pay” (Ecclesiastes 5:4-5).
Because vows are most usually made in haste and out of emotional adrenaline rather than logical thoughts; and since vows cannot be broken it can create a syrup sticky situation. Jephthah is a good Example of why the people of God should steer away from vows.
sacrifice as a burnt offering!?! (Judges 11:28-31). Of course he won the battle and guess who came to greet him: “And Jephthah came to Mizpeh unto his house, and, behold, his daughter came out to meet him with tumbrels’ and with dances: and she was his only child; beside her he had neither son nor daughter” (Judges 11:32-40).
“If a man vow a vow unto the LORD, or swear an oath to bind his soul with a bond; he shall not break his word, he shall do according to all that proceedeth out of his mouth. If a woman also vow a vow unto the LORD, and bind herself by a bond, being in her father's house in her youth; And her father hear her vow, and her bond wherewith she hath bound her soul, and her father shall hold his peace at her; then all her vows shall stand, and every bond wherewith she hath bound her soul shall stand. But if her father disallow her in the day that he heareth; not any of her vows, or of her bonds wherewith she hath bound her soul, shall stand: and the LORD shall forgive her, because her father disallowed her. And if she had at all an husband, when she vowed, or uttered ought out of her lips, wherewith she bound her soul; And her husband heard it, and held his peace at her in the day that he heard it: then her vows shall stand, and her bonds wherewith she bound her soul shall stand. But if her husband disallowed her on the day that he heard it; then he shall make her vow which she vowed, and that which she uttered with her lips, wherewith she bound her soul, of none effect: and the LORD shall forgive her. But every vow of a widow, and of her that is divorced, wherewith they have bound their souls, shall stand against her. And if she vowed in her husband's house, or bound her soul by a bond with an oath; And her husband heard it, and held his peace at her, and disallowed her not: then all her vows shall stand, and every bond wherewith she bound her soul shall stand... Every vow, and every binding oath to afflict the soul, her husband may establish it, or her husband may make it void. But if her husband altogether hold his peace at her from day to day; then he establisheth all her vows, or all her bonds, which are upon her: he confirmeth them, because he held his peace at her in the day that he heard them. But if he shall any ways make them void after that he hath heard them; then he shall bear her iniquity. These are the statutes, which the LORD commanded Moses, between a man and his wife, between the father and his daughter, being yet in her youth in her father's house” (Numbers 30:2-16).
This vow exception is why Adam could have not eaten the fruit of the tree of knowledge of good and evil; and he would have saved the creation, although Eve had already eaten as i mentioned in the post: http://studythebiblenotthesermon.blogspot.com/2009/11/fall-of-humanity.html
Even this exception has boundaries, the father must hear the vow, and disallow it in the day that he heard it, in order to annul it. The man can still disallow the vow afterwards, but then he will have to bear the woman’s sin for breaking a vow.